Don't allow overwriting a parent of the profile directory

__test__/backup.test.ts

@@ -168,7 +168,7 @@ describe("Backup", function () {
     });
 
     it(`relative paths`, async () => {
-      const backupPath = "../";
+      const backupPath = "../foo";
       /* prettier-ignore */
       when(spyOnsSettingsValue)
       .calledWith("path").mockImplementation(() => Promise.resolve(backupPath));

__test__/help.test.ts

@@ -148,12 +148,25 @@ describe("Test helper", function () {
   });
 
   test.each([
-    [ "/tmp/this/is/a/test", "/tmp/this/is/a/test", true ],
-    [ "/tmp/test", "/tmp/test///", true ],
-    [ "/tmp/te", "/tmp/test", false ],
-    [ "a", "/a", false ],
-    [ "/a/b", "/b/c", false ],
-  ])("pathsEquivalent (%s ?= %s)", (path1, path2, expected) => {
-    expect(helper.pathsEquivalent(path1, path2)).toBe(expected);
-  });
+    // Equality
+    ["/tmp/this/is/a/test", "/tmp/this/is/a/test", true],
+    ["/tmp/test", "/tmp/test///", true],
+
+    // Subdirectories
+    ["/tmp", "/tmp/test", true],
+    ["/tmp/", "/tmp/test", true],
+    ["/tmp/", "/tmp/..test", true],
+    ["/tmp/test", "/tmp/", false],
+
+    // Different directories
+    ["/tmp/", "/tmp/../test", false],
+    ["/tmp/te", "/tmp/test", false],
+    ["a", "/a", false],
+    ["/a/b", "/b/c", false],
+  ])(
+    "isSubdirectoryOrEqual (is %s the parent of %s?)",
+    (path1, path2, expected) => {
+      expect(helper.isSubdirectoryOrEqual(path1, path2)).toBe(expected);
+    }
+  );
 });

src/Backup.ts

@@ -295,10 +295,10 @@ class Backup {
       await this.showError(i18n.__(errorId, invalidBackupPath));
     };
 
-    if (helper.pathsEquivalent(profileDir, this.backupBasePath)) {
-      await handleInvalidPath("msg.error.backupPathJoplinDir");
-    } else if (helper.pathsEquivalent(os.homedir(), this.backupBasePath)) {
-      await handleInvalidPath("msg.error.backupPathHomeDir");
+    if (helper.isSubdirectoryOrEqual(this.backupBasePath, os.homedir())) {
+      await handleInvalidPath("msg.error.backupPathContainsHomeDir");
+    } else if (helper.isSubdirectoryOrEqual(this.backupBasePath, profileDir)) {
+      await handleInvalidPath("msg.error.backupPathContainsJoplinDir");
     }
   }
 

src/helper.ts

@@ -67,9 +67,21 @@ export namespace helper {
     return result;
   }
 
-  export function pathsEquivalent(path1: string, path2: string) {
-    // We use `resolve` and not `normalize` because `resolve` removes trailing
-    // slashes, while `normalize` does not.
-    return path.resolve(path1) === path.resolve(path2);
+  // Doesn't resolve simlinks
+  // See https://stackoverflow.com/questions/44892672/how-to-check-if-two-paths-are-the-same-in-npm
+  // for possible alternative implementations.
+  export function isSubdirectoryOrEqual(parent: string, possibleChild: string) {
+    // Appending path.sep to handle this case:
+    //   parent: /a/b/test
+    //   possibleChild: /a/b/test2
+    // "/a/b/test2".startsWith("/a/b/test") -> true, but
+    // "/a/b/test2/".startsWith("/a/b/test/") -> false
+    //
+    // Note that .resolve removes trailing slashes.
+    //
+    const normalizedParent = path.resolve(parent) + path.sep;
+    const normalizedChild = path.resolve(possibleChild) + path.sep;
+
+    return normalizedChild.startsWith(normalizedParent);
   }
 }

src/locales/de_DE.json

@@ -13,7 +13,7 @@
       "Backup": "Backup Fehler für %s: %s",
       "fileCopy": "Fehler beim kopieren von Datei/Ordner in %s: %s",
       "deleteFile": "Fehler beim löschen von Datei/Ordner in %s: %s",
-      "backupPathJoplinDir": "Als Sicherungs Pfad wurde das Joplin profile Verzeichniss (%s) ohne Unterordner ausgewählt, dies ist nicht erlaubt!",
+      "backupPathContainsJoplinDir": "Als Sicherungs Pfad wurde das Joplin profile Verzeichniss (%s) ohne Unterordner ausgewählt, dies ist nicht erlaubt!",
       "BackupSetNotSupportedChars": "Der Name des Backup-Sets enthält nicht zulässige Zeichen ( %s )!",
       "passwordDoubleQuotes": "Das Passwort enthält \" (Doppelte Anführungszeichen), diese sind wegen eines Bugs nicht erlaubt. Der Passwortschutz für die Backups wurde deaktivert!"
     }

src/locales/en_US.json

@@ -13,8 +13,8 @@
       "Backup": "Backup error for %s: %s",
       "fileCopy": "Error on file/folder copy in %s: %s",
       "deleteFile": "Error on file/folder delete in %s: %s",
-      "backupPathJoplinDir": "The backup path is the Joplin profile directory (%s) without subfolders, this is not allowed!",
-      "backupPathHomeDir": "The backup path is the home directory (%s). Either enable \"createSubfolders\" or choose a different backup directory.",
+      "backupPathContainsJoplinDir": "The backup path is or contains the Joplin profile directory (%s) without subfolders, this is not allowed!",
+      "backupPathContainsHomeDir": "The backup path is or contains the home directory (%s). Without enabling the subfolder setting, this is not allowed!",
       "BackupSetNotSupportedChars": "Backup set name does contain not allowed characters ( %s )!",
       "passwordDoubleQuotes": "Password contains \" (double quotes), these are not allowed because of a bug. Password protection for the backup is deactivated!"
     }